Acrotonic, mesotonic, basitonic (Branching patterns-Acrotonic, mesotonic, basitonic)study of thyme along water gradient.

In hot and dry habitats, higher proportion of basitonic individuals than in colder and humid habitats.
Mesotonic and acrotonic individuals relatively more present in colder and more humid habitat.

In stressed environments, thyme tends to go back to the bottom of the main stem to branch again.

These forms may therefore have functional advantages according to the habitat where they grow: competition for light, herbivores (haven't foud herbivores on Cistaceae yet).
Abiotic factors: soil, temperature, humidity, etc.

While there are contrasting conditions between the 2 habitat types, it might be that low-light environments, favoring tall herbs, might enter in competition for light, pushes thyme to have an acrotonic and mesotonic architecture, to position their crown above the herbaceous species

Architectural differences and variability in the relationship with light between open - closed environments in savanna: basitonic architectures capable of lateral spreading, effectively occupying space around them.

Keep in mind: unsure if the variation observed here is plasticity or genetic variation

Delayed reiteration process: plant’s response to injury and traumatism (loss / death of meristems, cavitation / embolism, disease, mechanical damage)

= More basitonic if high stress or disturbance (Branching patterns in Thymus vulgaris, Branching patterns-Acrotonic, mesotonic, basitonic)

Based on barthelemyPlantArchitectureDynamic2007

"Orthotropy (Fig. 14A; Frank, 1868; Koriba, 1958) refers to axes whose general orientation is vertical and whose symmetry is radial, with leaves in a spiral, opposite or verticillate disposition, and associated lateral branches arranged in all spatial directions. Plagiotropic axes (Fig. 14B; Frank, 1868; Koriba, 1958) have a general horizontal to slanted orientation and a bilateral symmetry owing to leaves (distichous phyllotaxis) and branches being generally arranged in one plane."

"In the latter case, one, two or more branches may develop after the death, abscission, abortion or transformation of the apex, and the resulting sympodial branching pattern be qualified respectively as mono-, di- or polychasial." Page 381

"Acrotony is the preferred development of lateral axes in the distal part of a parent axis or shoot" Page 383

"Orthotropy (Fig. 14A; Frank, 1868; Koriba, 1958) refers to axes whose general orientation is vertical and whose symmetry is radial, with leaves in a spiral, opposite or verticillate disposition, and associated lateral branches arranged in all spatial directions. Plagiotropic axes (Fig. 14B; Frank, 1868; Koriba, 1958) have a general horizontal to slanted orientation and a bilateral symmetry owing to leaves (distichous phyllotaxis) and branches being generally arranged in one plane." Page 384

Orthotropy and plagiotropy
Branching patterns-Acrotonic, mesotonic, basitonic

Open: light is not a selective pressure on tree growth form
Greater variation in tree forms is expressed
Fire frequency: selective for vertical growth (not important for our case)

Closed: heavy browsing selects for lateral growth

Shade vs open: Can be linked with Differences in ortho-plagiotropy in sun vs shade individuals and functional implications,

For a given plant height, individuals with larger conduits would be more vulnerable than individuals with narrower conduits (gleasonWeakTradeoffXylem2016, considering that Conductivity - safety trade-off is somewhat accurate).

With moist conditions, there is less risk of embolism, permitting wider conduits.

Based on the principle that Plant height is linked to wider conduits:
Once drought hits, big conduits with excessive size given the circumstances, become unusable --> re-sprouting at lower heights is therefore preferred. This gives for narrower, more embolism-resistant conduits better-suited for drier conditions.

Negatively correlated to root diameter in this study: goes against previous study (Newman, 1973), who reported that Kth did not correlate with root anatomical features.

Architectural differences and variability in the relationship with light between open - closed environments in savanna
In this study, savanna species responded to the shading treatment, while forest species were not impacted.

Forest species might be storing reserves in their stems rather than in their roots
While fire is the dominant factor shaping savanna seedling performance in comparison to forest species, competition for light is important to consider --> present in both ecosystems.

Concerning shape:
Cylindrical stem is better to go into great heights (more important for trees)
Conical shape (thicker) is good for reducing stem biomass loss through fires
Thicker might be better to reduce water stress?

"This is a ratio of the length of the longest branch (shoot length) and the total length of all the shoots on the branch unit (total length) (see Fig. 1). It is a measure of ramification and indicates whether growth is in the form of shoot elongation or lateral branching for each tree. It was measured on a randomly chosen branch of standard basal diameter 1.2 cm. Precision: 5 cm".